Solid state memory devices, or solid-state “disks,” are replacing some magnetic hard drives as a storage medium, especially in mass storage applications. Solid state memory devices typically share the same features as magnetic hard drives, such as write protection features. Write protection techniques are used to ensure integrity of data files so they remain uncorrupted. Hard disk drives usually provide switching mechanisms to disable writing to, for example, prevent hackers from corrupting executable instructions or data files.
Nonvolatile solid state memory technologies, such as Flash memory and EEPROM technologies, are commonly used as solid state memory for data storage and computer memory. Solid state storage devices that use these memories also implement structures to protect against unauthorized writing to code files and mass storage data files. Conventionally, Flash memory-based and EEPROM-based storage devices include write protect structures to prevent writing to main memory.
While traditional write protection approaches are functional, they have their drawbacks. First, Flash memory-based storage devices usually use nonvolatile register structures to store data configured to prevent writing to memory. These structures typically increase the size of die as the granularity of write protection decreases. That is, the fewer memory cells that a bit of a nonvolatile register structure protects, such as in a byte of data, the more nonvolatile register bits are required for protecting the memory cells overall. As such, die sizes of conventional memory technologies and the amount of memory protected by a bit are inversely proportional. To minimize increases in die sizes, memory designers generally use one nonvolatile register bit to protect a block of memory, which might be an inflexible limitation for some applications. Another drawback is that the traditional nonvolatile register structures implement memory technologies, such as Flash memory and EEPROM, that require erase cycles. These erase cycles delay modification of the nonvolatile register bits, which, in turn, stalls operation of the storage device until the protection bits can be updated. Third, Flash-base memory storage devices also require Flash file management systems and code, which consumes resource. Fourth, other write protection enhancement circuits, including write protection-related memory, typically affect the die size as well.
There are continuing efforts to improve techniques, systems, and devices for protecting data stored in memory.
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